Does flipping a reaction change the sign of the value of E or is it a completely different value?

For example if I have the value for the half reaction $\ce{Cl2 + 2e- -> 2Cl-}$ but need the value for the opposite reaction ($\ce{2Cl -> Cl2 + 2e-}$), do I just put a negative sign and treat it like $\Delta H$ values?